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AT45DB021A-RI Datasheet(PDF) 3 Page - ATMEL Corporation |
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AT45DB021A-RI Datasheet(HTML) 3 Page - ATMEL Corporation |
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3 / 28 page  AT45DB021A 3 Memory Architecture Diagram Device Operation The device operation is controlled by instructions from the host processor. The list of instructions and their associated opcodes are contained in Tables 1 through 4 (pages 8 and 9). A valid instruction starts with the falling edge of CS fol- lowed by the appropriate 8-bit opcode and the desired buffer or main memory address location. While the CS pin is low, toggling the SCK pin controls the loading of the opcode and the desired buffer or main memory address location through the SI (serial input) pin. All instructions, addresses, and data are transferred with the most signifi- cant bit (MSB) first. Buffer addressing is referenced in the datasheet using the terminology BFA8 - BFA0 to denote the nine address bits required to designate a byte address within a buffer. Main memory addressing is referenced using the terminology PA9 - PA0 and BA8 - BA0 where PA9 - PA0 denotes the 10 address bits required to designate a page address and BA8-BA0 denotes the nine address bits required to desig- nate a byte address within the page. Read Commands By specifying the appropriate opcode, data can be read from the main memory or from either one of the two data buffers. The DataFlash supports two categories of read modes in relation to the SCK signal. The differences between the modes are in respect to the inactive state of the SCK signal as well as which clock cycle data will begin to be output. The two categories, which are comprised of four modes total, are defined as Inactive Clock Polarity Low or Inactive Clock Polarity High and SPI Mode 0 or SPI Mode 3. A separate opcode (refer to Table 1 on page 8 for a complete list) is used to select which category will be used for reading. Please refer to the “Detailed Bit-level Read Timing” diagrams in this datasheet for details on the clock cycle sequences for each mode. CONTINUOUS ARRAY READ: By supplying an initial starting address for the main memory array, the Continu- ous Array Read command can be utilized to sequentially read a continuous stream of data from the device by simply providing a clock signal; no additional addressing informa- tion or control signals need to be provided. The DataFlash incorporates an internal address counter that will automati- cally increment on every clock cycle, allowing one continuous read operation without the need of additional address sequences. To perform a continuous read, an opcode of 68H or E8H must be clocked into the device fol- lowed by 24 address bits and 32 don’t care bits. The first five bits of the 24-bit address sequence are reserved for upward and downward compatibility to larger and smaller density devices (see Notes under “Command Sequence for Read/Write Operations” diagram). The next 10 address bits (PA9 -PA0) specify which page of the main memory array to read, and the last nine bits (BA8 - BA0) of the 24-bit address sequence specify the starting byte address within the page. The 32 don’t care bits that follow the 24 address bits are needed to initialize the read operation. Following the 32 don’t care bits, additional clock pulses on the SCK pin will result in serial data being output on the SO (serial output) pin. SECTOR 0 = 8 Pages 2112 bytes (2K + 64) SECTOR 1 = 248 Pages 65,472 bytes (62K + 1984) Block = 2112 bytes (2K + 64) 8 Pages SECTOR 0 Page = 264 bytes (256 + 8) PAGE 0 PAGE 1 PAGE 6 PAGE 7 PAGE 8 PAGE 9 PAGE 1022 PAGE 1023 PAGE 14 PAGE 15 PAGE 16 PAGE 17 PAGE 18 PAGE 1021 SECTOR ARCHITECTURE BLOCK ARCHITECTURE PAGE ARCHITECTURE BLOCK 0 BLOCK 1 BLOCK 30 BLOCK 31 BLOCK 32 BLOCK 33 BLOCK 126 BLOCK 127 BLOCK 62 BLOCK 63 BLOCK 64 BLOCK 65 BLOCK 2 SECTOR 2 = 256 Pages 67,584 bytes (64K + 2K) SECTOR 3 = 512 Pages 135,168 bytes (128K + 4K) |
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